It is common for torque limiting devices to be provided on machinery which is subject to mishaps that can damage the equipment. By way of example, packing machinery which packages bottles or other containers in cartons typically includes folding arms for folding the carton flaps. It is not unusual for a container to be mispositioned in the carton, and this can prevent the folding arms from completing the folding operation. In order to prevent the arms from being forced and possibly damaged in this situation, a torque limiter can be provided in the drive system for the arms. The torque limiter is normally set to slip or otherwise release the components of the drive system at a torque level above the normal torque level that is applied when the equipment is operating properly. Thus, the torque transmission is stopped when undue torque is applied, and damaged to the arms and other equipment is avoided.
More complicated devices known as single position torque limiters are often required. If the equipment includes a conveyor or other machinery which must be synchronized with the operation of the folding arms, it is necessary for the torque limiter to reengage the drive system a single rotation after disengagement in order to preserve the proper timing relationship. Random reengagement or reengagement at a time other than when a complete cycle has occurred would throw off the synchronization required for proper operation of the equipment. Devices which reengage properly after a cycle has been skipped are referred to as single position torque limiters.
While there have been single position torque limiting devices available in the past, they have not been altogether satisfactory. The mechanisms that are required are typically somewhat complicated and thus costly and subject to expensive maintenance and repair requirements. In addition, torque limiting devices tend to be large and bulky. This not only leads to space requirements that create problems in many applications, but it also results in high costs due to the need for larger parts.